In a variety of orthopedic procedures, a section of bone tissue is removed and an orthopedic prosthesis is attached. For example, it has become relatively common to replace one or more components of a knee joint. One such prosthetic device is mounted to the distal end of a femur. Typically, several cuts are made through the bone tissue at the distal end of the femur to properly shape the bone for receipt and mounting of the prosthetic device.
However, the prosthetic device must be properly sized relative to the size of the femur to which it is attached or the strength and/or comfort of the implant can be compromised. For example, one of the sizing cuts typically is made along the anterior cortex of the femur. If the size of the implant is too small relative to the area of the cut, a “notch” is left along the bone tissue at the peripheral edge of the implanted prosthetic device. This notch can weaken the bone, making it susceptible to fracture. If, on the other hand, the implant is too large relative to the area of the cut, the anterior tip of the prosthetic device can overhang the face of the bone. This creates a gap between the implant and the bone tissue potentially resulting in reduced strength at the point of attachment between the implant and the bone tissue. Also, if the implant overhangs the bone tissue, the patient may incur soft tissue irritation.
Examples of current techniques for sizing such prosthetic devices include visually estimating the size of the cuts once a femoral cutting block or guide is fixed into position; comparing the implant to femoral drill guides; and using presurgical X-rays in conjunction with implant X-ray templates to estimate proper implant size. However, these methods involve substantial estimation by the practitioner and create difficulty in producing consistent, accurate sizing of the implant.